The present invention relates to a communication charge management system for managing the communication charge in units of telephone sets and, more particularly, to a communication charge management system in which a specific telephone set, i.e., a master telephone set manages the communication charge of the subsidiary telephone set.
Generally, in a public telephone set, the user pays the call or communication (to be referred to as communication hereinafter) charge by coins or a prepaid card every communication. In a general subscriber's telephone set, communication charges are accumulated in units of predetermined periods, e.g., in units of months, and the bill is issued to the subscriber after the predetermined period.
In the public telephone set, the communication charge is managed every communication, the user performs communication within the user's coins or prepaid card, and thus the communication charge does not become in a large sum. In the general subscriber's telephone set, however, since charges within a predetermined period are accumulated and made, a bill in a large sum may be issued after the predetermined period. Particularly when one telephone set is commonly used by a plurality of users, one telephone line is commonly used by a plurality of telephone sets, or the communication charges of telephone sets by different users are made to a representative subscriber, the communication charge in a large sum may be unexpectedly made.
To prevent this, according to the technique disclosed in Japanese Patent Publication No. 60-041503, a communication charge limit within a predetermined period is set for a switching unit in units of telephone sets or groups of specific telephone sets. When the communication charge exceeds the set charge limit before the predetermined period, an alarm sound that the communication charge exceeds the charge limit is generated to disconnect communication and restrict a subsequent outgoing call.
According to the technique disclosed in Japanese Patent Laid-Open No. 4-181855, the telephone set is operated to store the type of communication restriction such as call restriction, the communication restriction charge, or date & time information in the telephone set. When toll call restriction is set, a call to a toll area is restricted. When restriction for one call charge is set to prevent the charge for one call from exceeding a predetermined charge, the line is forcibly disconnected when the charge exceeds the set charge. In this technique, communication charge restriction can be set to limit the sum of past and current communication charges to a predetermined charge. Also in this case, the line is disconnected when the charge exceeds the predetermined charge.
Japanese Patent Laid-Open No. 62-15961 also discloses the technique of accumulating and managing communication charges. According to this technique, when a call is made to a specific telephone number, e.g., a telephone number dedicated for a specific individual (child), a long-time outgoing call can be disconnected.
According to the technique disclosed in Japanese Patent Laid-Open No. 5-284255, the ISDN (Integrated Service Digital Network) terminal is operated to store the charge limit and a telephone number subjected to originating restriction/originating restriction cancellation in the ISDN terminal. In the ISDN terminal, charges are accumulated every communication. When the accumulated charge exceeds a predetermined charge limit, an origination to a telephone number subjected to originating restriction is restricted but that to only a telephone number subjected to originating restriction cancellation is permitted.
According to the technique disclosed in Japanese Patent Laid-Open No. 61-263355, the digital telephone set is operated to store "communication charge limit for each local call", "communication charge limit for each toll call", "total communication charge limit of local calls", "total communication charge limit of toll calls", and "communication charge limit for each origination telephone number" in the telephone set. Whether the communication charge exceeds the charge limit is monitored based on the charge informed from the telephone network to the digital telephone set during or at the end of communication. When the communication charge exceeds the charge limit, the digital telephone set generates an alarm sound and disconnects the line.
Recently, portable telephones have become popular, and a plurality of telephone sets are owed by one family. Along with variations in individual information collection range and communication contents, each member of one family tends to own his/her own telephone set. In this situation, a specific individual (child) of the family makes a call or calls in a large sum, and as a result the subscriber (parent) receives a bill in a large sum.
To solve this problem, the subscriber must appropriately grasp the use states of a plurality of telephone sets within a specific group. However, the above conventional techniques can only manage the communication charge of a specific telephone set, or can only set the communication charge limit of the whole group and manage the charge. They cannot appropriately manage the communication charges for only telephone sets owed by individuals having a special relationship (master-slave relationship) such as the relationship between a subscriber (parent) and a specific individual (child).